This invention relates to the control of industrial processes, and in particular a method and a system for the control of an industrial process based on an examination of observed variables obtained from a sample of products which are indicative of the properties of the product generated by the process and correlated with the set process parameters. More specifically it relates to a method and system for statistical control in which the sample size needed to obtain reliable and stable information about the properties of the product is calculated through observing one or more selected variables on the basis of data obtained from a pilot sample.